Background: CD11b belongs to the integrin family and is expressed on neutrophils, monocytes, natural killer cells, and a subset of lymphocytes. Although CD11b expressed on neutrophils and monocytes has been extensively investigated and has been reported to play an important role in the migration of these subsets of leukocytes, the function of CD11b expressed on a subset of B cells has not yet been clarified.
Objective: To elucidate the functional activity of CD11b expressed on B cells, we characterized the CD11b-expressing cells among the B-cell population and investigated their migratory ability.
Methods: Isolated peripheral blood CD19 + B cells were analyzed by flow cytometry. The migratory ability of B cells was evaluated by the transwell assay, and the contribution of CD11b to this ability was investigated by using an anti-CD11b blocking mAb.
Results: The majority of CD27 - IgD + naive B cells were CD11b - , whereas most CD27 + memory cells were CD11b +. Among the CD27 + memory cells, expression of CD11b was stronger on the IgD - cells than on the IgD + cells. In the transwell assay, the migrating cells were predominantly CD27 + IgD - cells, most of which expressed CD11b. The addition of an anti-CD11b blocking mAb resulted in the significant reduction of the number of migrating B cells.
Conclusion: Memory B cells express CD11b and, in contrast with naive B cells, have high migratory ability. CD11b plays an essential role in the homing process of memory cells.